Efficacy and Safety of Nasal Immunisation with Somatostatin DNA Vaccine for Growth Promotion in Fattening Pigs

SIMPLE SUMMARY: Growth qualities are critical economic traits that substantially impact pork yield. Here, we evaluated the effect of somatostatin (SS) DNA vaccines on growth promotion in fattening pigs. Our results demonstrate that immunisation with SS DNA vaccine induces cellular and humoral immunity in fattening pigs, producing anti-SS antibodies that neutralise endogenous SS, thereby promoting daily gain and slaughter weight. In addition, the vaccine does not pose a safety challenge. Consequently, it is possible to accelerate the growth of fattening pigs through the immune SS DNA vaccine, which will bring more economic benefits to the company and the farmer. ABSTRACT: This study aimed to evaluate the efficacy and safety of the SS DNA vaccine on growing pigs. Randomly, 147 pigs were divided into four groups, treatment 1 (T1, 3 × 10(9) CFU/mL, n = 39), T2 (3 × 10(8) CFU/mL, n = 35), T3 (3 × 10(7) CFU/mL, n = 35) and control group (phosphate-buffered saline, n = 38). All animals received two vaccinations separated by 45 days and the same diet and management. The results showed that all treatment groups (T1, T2 and T3) had significantly higher slaughter weight (d 185) than the Ctrl group (p < 0.05), and daily gain between 50 and 110 days of age was significantly higher in all treatment groups than in the Ctrl group (p < 0.05). Antibody-positive pigs have significantly higher daily weight gain than that in antibody-negative pigs (p < 0.05). The results of the meat quality analysis showed no significant changes between the P (antibody-positive pigs) and N (antibody-negative pigs) groups. Furthermore, the results showed that antibody titres at 110 and 185 days had a significant positive correlation with the daily weight gain (p < 0.05) and a significant negative correlation with the backfat thickness (p < 0.05). Evaluating the safety of vaccines by PCR amplification of target genes (GS/2SS), faecal, soil and water samples had no target genes detected by PCR amplification in these samples after 5 days, and no GS/2SS were detected in the blood and tissues for the experimental period. Moreover, no abnormalities were found in pathological sections of the P group compared with the N group. In conclusion, SS DNA vaccines can promote the growth of fattening pigs to a certain extent without altering the meat quality, and it has no effects on the safety of the surrounding environment.